void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, STM32!");
  pinMode(PA0, INPUT_PULLDOWN);
  pinMode(PA1, INPUT_PULLDOWN);
  pinMode(PA2, INPUT_PULLDOWN);
  pinMode(PB0, OUTPUT);
}

int summe;

void loop() {
  summe = digitalRead(PA0) + digitalRead(PA1) + digitalRead(PA2);
  if(summe==1 || summe==3){
    digitalWrite(PB0,LOW);
  }
  else{
    digitalWrite(PB0,HIGH);
  }
  delay(10); // this speeds up the simulation
}